Patient Prosthesis Mismatch and Strategies to Prevent It During by mikesanye

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									                                                                                                            Hellenic J Cardiol 2010; 52: 41-51



Review Article
                           Patient-Prosthesis Mismatch and Strategies to
                           Prevent It During Aortic Valve Replacement
                           Efstratios apostolakis1, Nikolaos G. Baikoussis1, Nikolaos a. papakoNstaNtiNou1,
                           JohN GoudEvENos2
                           1
                             Cardiothoracic Surgery Department, Patras University School of Medicine, University Hospital of Patras, Rion
                           Patras, 2Department of Cardiology, University of Ioannina School of Medicine, Ioannina, Greece




                           A
Key words: Aortic                   ortic valve replacement (AVR) is                   observed phenomenon without relevant
valve stenosis, aortic              the well established treatment for                 clinical implications,10-12 many others have
valve replacement,
prosthesis-patient
                                    patients with severe aortic valvu-                 argued that it occurs frequently and has
mismatch, stentless        lar stenosis (AVS). It decreases (or elimi-                 important clinical consequences.8,13-16 We
bioprosthesis.             nates) the pressure gradient between the                    reviewed the international bibliography
                           left ventricle and ascending aorta and con-                 and in this report we focus on the aetiol-
                           sequently leads to a gradual regress of left                ogy, pathophysiology and prevention of
                           ventricular (LV) hypertrophy. 1,2 LV hy-                    PPM.
                           pertrophy caused by severe aortic valve
                           stenosis is associated with a high risk of
                                                                                       Aetiology of PPM
                           sudden death, congestive heart failure,
                           and stroke.1 On the other hand, incom-                      The phenomenon of PPM is mainly attrib-
                           plete regression of LV hypertrophy after                    uted to two main reasons. First, patients
                           AVR has been shown to significantly re-                     with aortic valve disease frequently exhib-
Manuscript received:       duce 10-year survival.2-4 The concept of                    it annulus calcification and fibrosis as well
August 26, 2010;           prosthesis-patient mismatch (PPM) was                       as LV hypertrophy, and these pathological
Accepted:
November 25, 2010.
                           first introduced by Rahimtoola in 1978                      processes can reduce the size of the aor-
                           as the situation in which “the effective                    tic annulus.1,3 In these situations a small
                           prosthetic valve area, after insertion into                 prosthesis—in relation to the patient’s
Address:                   the patient, is less than that of a normal                  body surface area (BSA)—should be im-
Nikolaos G. Baikoussis
                           human valve”. 5 In other words, PPM is                      plantated.8 Second, because the stented
Kolokotroni 4, Messatida   deemed to occur when the effective orifice                  prosthesis is inserted within the aorta and
26500 Patras, Greece       area of the implanted prosthetic valve is                   has its own annulus, the effective orifice
e-mail: ngbaik@yahoo.com   too small in relation to the patient’s body                 area (EOA) after implantation is neces-
                           size, despite normal prosthesis function,                   sarily smaller than that of a normal native
                           resulting in an abnormally high postoper-                   valve.1,2 In fact, it has been shown that the
                           ative pressure gradient.6-8 By this defini-                 EOA available for blood flow represents
                           tion, nearly all patients receiving a pros-                 only 40% to 70% of the total area occu-
                           thetic aortic valve will have some degree                   pied by the valve. 17 However, the stent-
                           of PPM, as the sewing ring, struts and                      less valves without a fixed annulus allevi-
                           leaflets of prostheses produce a relative                   ate this problem, and they generally pro-
                           obstruction to blood flow. 1,9 Although                     vide a larger valve EOA in relation to the
                           some authors claim that PPM is a rarely                     patient’s BSA, as compared with stented

                                                                                                      (Hellenic Journal of Cardiology) HJC • 41
E. Apostolakis et al

bioprostheses. 18-21 The EOA is a physiological pa-        much higher gradients.35-37 Factors that may predict
rameter that represents the minimal cross-sectional        PPM preoperatively are as follows: larger BSA, high
area of the trans-prosthetic blood flow jet, and is eas-   BMI, older age, smaller prosthesis size, and valvular
ily measured by Doppler echocardiography. The only         stenosis as the predominant lesion before the oper-
parameter that has been validated to identify PPM is       ation.38-40 It is observed that PPM occurs more fre-
the ‘indexed’ EOA, that is, the EOA of the prosthesis      quently in patients with stenotic native valves and in
divided by the patient’s BSA (indexed EOA = EOA/           older patients. This is consistent with the overall con-
BSA).7,22-24 Reference values for EOA data exist for       cept, because patients with stenotic native valves gen-
each type and size of prosthesis, and they should ide-     erally have a smaller valvular annulus than those with
ally be derived from in vivo rather than in vitro val-     regurgitant valves,41 while calcific aortic stenosis is by
ues.8,14                                                   far the most prevalent lesion in older patients under-
     Internal geometric area (IGA) is another ana-         going AVR.8
tomical parameter calculated from the static mea-
surement of the internal diameter of the prosthe-
                                                           Pathophysiologic consequences of PPM
sis. Unfortunately, IGA measurement varies from
one type of prosthesis to the other, while the ratio       It has been shown that PPM has a significant im-
between the EOA and the geometric area also var-           pact on important clinical outcomes, such as free-
ies widely from one type and/or size of prosthesis         dom from heart failure, LV mass regression and late
to another.10,14,25 Notably, although these measure-       survival, and that this impact is highly modulated by
ments are reproducible without significant variabil-       the functional status of the LV before surgery.8,13,42,43
ity, they have consistently been shown to be unre-         The temptation to conclude that PPM is an impor-
lated to either postoperative gradients 26 or clini-       tant consideration only in patients with impaired
cal outcomes.10,12,27-29 In fact, Koch et al29 reported    LV function and can almost be dismissed as irrel-
identical values for indexed IGA in patients with          evant in patients with normal function should, how-
stented pericardial valves and patients with homo-         ever, be avoided. 6 The impact of PPM on clinical
grafts, whereas peak and mean pressure gradients           outcomes might well be at least as important as that
were twice as high in the former as in the latter. In      of LV function.6,44 It has been reported that a small
addition, they found no relation between the indexed       decrease in indexed EOA may correspond to a large
IGA and the clinical outcome of functional recovery        increase in transvalvular pressure gradient,5,7,8,18,38 to
after surgery.                                             less regression of LV hypertrophy, and to decreased
     Generally, haemodynamic compromise occurs             survival after AVR.42,43,45 Indeed, the extent of post-
when the indexed EOA of the prosthetic valve is cal-       operative LV mass regression has been shown to be
culated to be less than 75% of the native EOA, lead-       highly dependent on the type and size of prosthe-
ing to high postoperative transvalvular gradients and      ses used for valve replacement, as well as on their
reduced regression of left ventricular hypertrophy.8       haemodynamic performance.43,46,47 According to Pi-
According to the commonly used definition, valve           barot et al,40 in patients with PPM and an indexed
PPM is characterized as severe for indexed EOA ≤0.6        EOA ≤0.85 cm2/m2 the trans-prosthetic gradient was
cm2/m2, moderate for values 0.6-0.85 cm2/m2, and mild      found to be 22 ± 8 mm Hg, compared with 15 ± 6
for values >0.85 or 90 cm2/m2.13,18,30-33 Interestingly,   mm Hg in patients without PPM. In addition, car-
after AVR severe PPM occurs in 2-11% of patients,          diac index, which was similar in patients with and
moderate PPM in 20-70%,23 while after a mechanical         without mismatch up to three years after the opera-
implantation the incidence of significant mismatch         tion, decreased significantly thereafter only in pa-
may reach 60%.34                                           tients with mismatch (-0.54 ± 0.32 vs. -0.17 ± 0.49
                                                           L/min/m2, p=0.04). Although the deterioration in
                                                           valve EOA was similar in both groups, during fol-
Prediction of PPM
                                                           low up the mean gradient increased significantly (6
Intraoperatively, a measured small prosthesis size is      ± 6 vs. 1 ± 1 mmHg) only in patients with PPM. The
a widely recognized aetiological factor for postopera-     greatest postoperative deteriorations in cardiac index
tively observed PPM. Consequently, a small valve im-       and gradients were seen in the patients with the most
planted in the aortic position—generally prosthetic        severe PPM (i.e. with an indexed EOA ≤0.65 cm2/
valves sized <20-21 mm (for an adult)—tend to have         m2).8,40

42 • HJC (Hellenic Journal of Cardiology)
                                                                Patient-Prosthesis Mismatch: Alternative Operative Techniques

Influence on LV mass and function                         Influence on operative mortality
As has been reported in many studies, there is a          According to Blais et al,14 the impact of PPM was
strong interaction between PPM and depressed LV           found to increase exponentially in relation to the de-
function with regard to early mortality after AVR,        gree of severity, to the extent that even patients with
and such an interaction also exists in relation to late   normal LV function were found to have a signifi-
mortality, heart failure, and LV mass regression. 14      cant increase in early mortality when faced with se-
The interaction between LV dysfunction and PPM            vere PPM. PPM associated with increased operative
is consistent with the concept that the increased LV      mortality after AVR, particularly when combined
afterload caused by PPM is less well tolerated in a       with LV dysfunction,14 can be predicted at the time
poorly functioning ventricle than in a normal ventri-     of surgery and measures can be taken to avoid severe
cle. Avoidance of PPM in patients with preoperative       PPM.26 These measures include performing an aor-
LV systolic dysfunction is, therefore, an important       tic annulus enlargement procedure,52,53 or choosing
priority.7 Regarding the expected LV mass regression      a prosthesis with a larger effective orifice area—al-
after AVR, Barner et al48 demonstrated that it is bet-    though such techniques may increase the complexity
ter in patients with a prosthesis size >21 mm (21%)       of the procedure and the operative mortality.9
than in patients with a prosthesis size ≤21 mm (8%).           Multi-centre data collected from 701 consecu-
Nishimura et al 42 found that the mean wall thick-        tive patients undergoing AVR showed that 30-day
ness of the LV after AVR was directly related to the      mortality was higher in those with PPM than in those
pressure gradient across the aortic prosthetic valve.     without PPM (15.2% vs. 3.4%). Severe PPM was
In a recent study of 1103 patients with a bioprosthe-     associated with increased early mortality by a fac-
sis, Del Rizzo et al49 found a strong relation between    tor of five to six times.9,54,55 Blais et al,14 in a simi-
the indexed EOA and the extent of LV mass regres-         lar study, found that severe PPM was associated with
sion. At three years after the operation, the LV mass     an 11.4-fold and 12.6-fold increase in early and late
index had decreased by 23%, on average, in patients       mortality by univariate and multivariate analysis, re-
whose indexed EOA was >0.8 cm2/m2, as compared            spectively.14 In another study of patients after AVR
with 4.5% in patients with an indexed EOA <0.8 cm2/       using bioprostheses, Rao et al showed that early
m2. In contrast, no difference was noted between the      mortality was higher in those with an indexed EOA
patients with an indexed EOA between 0.8 and 1.0          ≤0.75 cm2/m2 (7.9% vs. 4.6%).56 Given that the LV is
cm2/m2 and those with an indexed EOA >1.0 cm2/m2          most vulnerable during the early postoperative peri-
(-24% vs. -22%).                                          od, it is intuitive to think that the increased afterload
                                                          posed by PPM may be particularly deleterious and
Influence on physical capacity                            may lead to excess mortality during this period.9 In
                                                          contrast to this, three other studies found no differ-
Postoperative improvement of the patient’s physical       ence in early mortality with PPM.10,30,57 Concerning
capacity is an important objective of AVR, because        the early 30-day morbidity (stroke, prolonged venti-
it directly influences the patient’s symptomatic sta-     lation, new renal failure, prolonged post-operative
tus, quality of life and rate of reemployment.2,50 In     stay, prolonged ICU stay or readmission) among pa-
addition, poor physical capacity is associated with a     tients with severe PPM after AVR, one study found
higher rate of late mortality after valve replacement.4   no association.9
De Carlo et al51 reported that, among patients with a
21 mm St. Jude mechanical valve, those with a BSA
>1.70 m2 had significantly lower exercise tolerance       Influence on late survival
than those with a BSA <1.70 m2. Furthermore, the
indexed valve EOA was an independent predictor            Previous short- and intermediate-term survival ana-
of exercise tolerance variables. On the other hand,       lyses have not consistently identified PPM as an in-
recent studies of patients with bioprosthetic aortic      dependent predictor of adverse outcomes.10,12 It is
valves showed that maximal exercise capacity, as esti-    therefore agreed that severe PPM increases early
mated by maximal workload, peak oxygen consump-           mortality, whereas its effect on late results is less
tion or anaerobic threshold, is similar when patients     clear. Clinically, severe PPM appears to be associated
with an indexed EOA ≤0.85 and >0.85 cm2/m2 are            with a higher incidence of late symptoms of heart fail-
compared.8,31                                             ure and less regression of LV hypertrophy, as deter-
                                                                                      (Hellenic Journal of Cardiology) HJC • 43
E. Apostolakis et al

mined by means of echocardiographic analysis.44,58,57        survival was 79 ± 1% at 5 years and 59 ± 2% at 10
Recently, an analysis from the Mayo Clinic identified        years. For patients with severe PPM, 5-year survival
severe PPM as an independent predictor of long term          (74 ± 8%) and 10-year survival (40 ± 10%) were sig-
mortality in patients with small aortic valve prosthe-       nificantly lower than for patients with non-significant
ses.13 However, it is important to note that only pa-        PPM (84 ± 1% and 61 ± 2%, respectively). There
tients with small valves (19 and 21 mm) were included        was also a trend towards lower survival in the severe
in that study. The study also excluded all short-term        PPM group when compared with the moderate PPM
deaths, which might have biased the results because          group (5-year survival: 81 ± 2%; 10-year survival: 57
short-term mortality is higher in patients with mod-         ± 3%) and in the moderate PPM group when com-
erate or severe PPM.13 However, several studies have         pared with the non-significant PPM group. Free-
shown that PPM was associated with an increased risk         dom from cardiovascular-related death was 92 ± 1%
of late mortality13,34,44,59,60 and the greatest mortality   at 5 years and 79 ± 2% at 10 years in the whole se-
risk was observed in patients with pre-existing LV sys-      ries, and was significantly lower in patients with se-
tolic dysfunction.14,44                                      vere PPM (5-year: 78 ± 7%; 10-year: 50 ± 11%)
     Although most, 11,14,59,61 but not all, 30 studies      than in those with moderate PPM (5-year: 90 ± 1%;
showed an impact of PPM on early mortality, the im-          10-year: 77 ± 3%) and in those with non-significant
portance of PPM for long-term survival is still un-          PPM (5-year: 93 ± 1%; 10-year: 81 ± 2%). Notably,
clear. Indeed, some authors 56,58,59 did identify mis-       severe PPM was more significant for patients >70
match as a significant risk factor for reduced long-         years-old, with BMI <30 kg/m2 and with LV ejection
term survival, but others did not support this find-         fraction (LVEF) <50%.60
ing.10-12,30 Among 469 adult patients who underwent
mechanical AVR for aortic stenosis and were fol-
                                                             Risk factors for operative and late mortality
lowed for a mean period of 7.9 years (interquartile
range 5.0-10.0 years) the degree of PPM was minimal          Several factors, including age, BMI, and preoper-
in 57%, moderate in 39%, and severe in only 4% of            ative LV functional status, may potentially influ-
patients.34 Seventy-five percent of severe PPM cases         ence the effect of PPM and the postoperative out-
occurred after implantation of smaller (i.e. 19 and          come.60,62 Some other risk factors could be advanced
21 mm) mechanical aortic valves. This severe mis-            age, elevated preoperative serum creatinine, elevat-
match occurred in 11% of all patients who received           ed mean pulmonary artery pressure, emergent in-
19 or 21 mm mechanical valves. Twelve-year surviv-           tervention and a long total bypass time. Severe PPM
al was 77% in patients with minimal mismatch, 63%            was not associated with stroke, prolonged ventila-
in those with moderate mismatch, and only 47% in             tion, new renal failure, prolonged postoperative stay,
those with severe mismatch.34 Another study of 533           prolonged ICU stay or readmission within 30 days,
patients who underwent AVR concerned the rela-               by univariate or multivariate analysis.9 One study60
tionship between the measured EOA within 10 days             has shown that PPM reduces survival in patients with
after operation and the follow up for a mean follow-         a BMI less than 30 kg/m2, but not in those who are
up time of 4.7 ± 2.2 years.45 According to that mea-         obese (BMI ≥30 kg/m2). This finding is most likely
surement, moderate and severe PPM were observed              related to the fact that the use of the body surface
in 52% and 28% of the patients, respectively. The            area for normalisation of EOA may overestimate the
adjusted survival rates at 5 and 7 years were 81 ± 4%        prevalence and severity of PPM in obese patients.60
and 65 ± 9% for patients with severe prosthesis-pa-              According to some reports, severe PPM has a
tient mismatch, 83 ± 3% and 69 ± 6% for patients             significant negative effect on late survival in young-
with moderate mismatch, and 90 ± 4% and 87 ± 7%              er patients.60,62 This finding might be related to the
for patients with mild mismatch at discharge, respec-        fact that younger patients have higher cardiac out-
tively. Notably, the main decrease in survival was ob-       put requirements. They certainly have higher basal
served after 5 years. In another study involving 2576        metabolic rates and are generally more physically ac-
pts undergoing AVR who were followed for a mean              tive. Also, because they have a longer life expectan-
follow-up of 4.8 ± 3.4 years (median 4.3 years; maxi-        cy, younger patients are exposed to the risk of PPM
mum 14 years), the patients were divided in 3 groups         for a longer period of time.11 A possible explanation
according to PPM severity: non-significant (67%),            for the late effect of PPM on survival could be that
moderate (31%), and severe (2%). 60 The total late           patients with PPM undergoing long-term biopros-

44 • HJC (Hellenic Journal of Cardiology)
                                                              Patient-Prosthesis Mismatch: Alternative Operative Techniques

thetic valve degeneration or development of pannus       which can easily be applied in the operating room, ac-
have less EOA “reserve” and will therefore develop       cording to the literature:8
severe stenosis of their valves more rapidly than pa-
                                                         •	 Step 1. Calculate the patient’s BSA from weight and
tients without PPM undergoing the same processes.
                                                            height using the equation or the chart, proposed by
Also, older patients might be more likely to die from
                                                            Dubois:64
other causes before this process has any impact. 11,60
                                                                  BSA = weight0.425 × height0.725 × 0.007184
Moderate-to-severe PPM (indexed EOA ≤0.85 cm2/
                                                         •	 Step 2. Ensure an indexed EOA >0.85, >0.80 or
m2) was also an independent predictor of late mor-
                                                            >0.75 cm2/m2, given the patient’s BSA as calculated
tality in patients with a preoperative LVEF <50%,
                                                            in step 1. The choice between 0.85, 0.80 and 0.75
but not in patients with preserved LV systolic func-
                                                            cm2/m2 is based on the minimal requirement for a
tion.60 Previous studies14 have shown increased early
                                                            given patient, with the knowledge that 0.85 cm2/m2
mortality in patients with a combination of moderate
                                                            or higher is the optimal value for better blood flow.8
PPM and LV dysfunction, as well as in all patients
                                                         •	 Step 3. Select the type and size of valve that has
with severe PPM, irrespective of LV function. Stud-
                                                            reference values for EOA greater than or equal
ies from other laboratories44,63 have also demonstrat-
                                                            to the minimal EOA value obtained in step 2.8
ed that the impact of moderate PPM on mid-term
mortality is more important in patients with pre-ex-     The reference values for EOA should therefore be
isting LV dysfunction than in those with preserved       readily available in the operating room to determine
LV function.                                             whether a particular prosthesis meets the require-
     According to one study,34 patient variables more    ments to avoid PPM. If not, the insertion of a larger
commonly associated with greater degrees of mis-         prosthesis size or that of a different type with a better
match included hypertension, increasing age, and         haemodynamic performance should be considered.8
higher BSA. Female sex was associated with more               However, strategies to avoid or reduce the sever-
severe mismatch; however, this association is prob-      ity of PPM should be individualised and should take
ably substantially confounded by the smaller pros-       into account multiple variables, such as age, BMI,
thetic valve sizes often used in female patients. No     lifestyle, LV function, LV hypertrophy, and the use
significant differences were found in other domains      of concomitant procedures.2,3,15 For example, if mod-
at baseline. Age greater than 65 years was an inde-      erate PPM is expected to occur in an elderly, seden-
pendent risk factor for long-term mortality. Because     tary patient with normal LV function, the benefits of
the population is ageing, the incidence of degenera-     doing an alternate procedure to avoid PPM might
tive aortic valve disease continues to grow, and the     be estimated to be outweighed by the inherent risks
potential adverse effect of PPM on long-term surviv-     or disadvantages of doing such a procedure. Preven-
al in the elderly population is of increasing concern.   tion of PPM becomes an important consideration
However, there was no interaction between age and        in a young, athletic individual, or if the patient has
PPM. Instead, PPM predicted long-term mortality          evidence of impaired LV function or severe LV hy-
regardless of patient age.34 Moderate or severe mis-     pertrophy. It has been emphasised that implanta-
match was most likely to occur in patients with larg-    tion of a small prosthesis does not necessarily result
er BSA, older age, and smaller prosthesis size. The      in PPM, and can be perfectly adequate in a patient
patients with substantial mismatch had significantly     with a small body size.7 In the case of an anticipated
worse long-term outcomes than those with minimal         PPM, alternate procedures may be included: a) aor-
mismatch.34                                              tic annulus enlargement14,52 to accommodate a larg-
                                                         er size of the same prosthesis model;8,60 b) insertion
                                                         of a prosthesis with a better haemodynamic perfor-
Therapeutic strategies
                                                         mance, such as a stentless bioprosthesis;8,60,65 c) im-
Prediction of mismatch at the time of surgery seems      plantation of a new generation stented or bileaflet
to be the optimal way to avoid PPM after AVR. Mod-       mechanical prosthesis implanted in a supra-annular
erate PPM should be avoided in young patients (less      position;60,66-68 d) homografts;8,14 or e) performance
than 65 years old), in patients who present with pre-    of a Ross operation.69 However, a considerable num-
operative LV dysfunction or severe LV hypertrophy,       ber of patients have also had mismatch after stent-
as well as in physically active individuals.7            less valve implantation, even after full root replace-
    To avoid PPM, an algorithm has been suggested        ment—although some of these cases are attributed

                                                                                    (Hellenic Journal of Cardiology) HJC • 45
E. Apostolakis et al

to technical reasons relating to the implantation pro-     PPM lower, in newer vs. older generations of prostheses,
cedure.70                                                  in mechanical vs. stented bioprosthetic valves, in supra-
    Despite over 30 years of investigations and clini-     annular vs. intra-annular stented bioprostheses, and in
cal applications, the ideal aortic valve substitute re-    stentless vs. stented bioprosthetic valves.37,52,86
mains elusive. Although conventional stented bio-
prostheses avoid the hazards of embolisation and
                                                           Stentless valves
anticoagulation, the rigid stent design increases the
likelihood of late structural failure and reoperation.71   Lower rates of severe PPM were observed after inser-
Furthermore, the obstructive nature of the stent leads     tion of stentless valves than after the use of stented
to a non-physiological flow pattern and residual pres-     biological valves.87 The advent of stentless biopros-
sure gradient,72 which—particularly in small valves—       theses represents a major advance, because these
may have an important bearing on postoperative left        prostheses generally have a much better haemody-
ventricular mass regression and function, with an ad-      namic performance than stented bioprostheses, both
verse clinical outcome.73,74 It has therefore been sug-    at rest and during exercise.19,65,88-91 Another option
gested by many studies that, in patients with a mea-       is the stentless aortic xenograft, which was first in-
sured aortic annulus diameter of 19 mm or smaller,         troduced into the clinical arena by Binet and associ-
prostheses with the largest actual orifice area pro-       ates91 in 1965. Despite excellent initial results, early
vided by the manufacturer,75,76 or other types of valve    enthusiasm waned because of premature structural
prostheses—i.e. stentless porcine,43,77-80 aortic homo-    deterioration as a consequence of the poor preserva-
graft,81 or pulmonary autograft42,82—should be con-        tion methods. This concept of using the aortic root
sidered.                                                   as a physiological stent for the valve prosthesis was
                                                           revived by David et al92 in 1987, when they initiated
                                                           a new trial using a stentless porcine aortic valve. In-
Aortic root replacement
                                                           deed, stentless bioprostheses provide a larger EOA in
In order to avoid PPM, patients could undergo an           relation to the patient’s BSA, resulting in a larger in-
aortic root enlargement procedure.83 The insertion         dexed EOA and a lower gradient.65
of a larger prosthesis may require enlargement of the           The superior haemodynamic performance of
aortic root,84 but the increased operative risk must be    stentless valves is due to the fact that, size for size,
taken under consideration.83 Some groups have suc-         their EOA is generally larger than that of stented
cessfully reduced the occurrence of PPM using aor-         valves. Moreover, for the stentless valves, a larg-
tic root enlargement, without any increase in opera-       er prosthesis can be inserted in a smaller annu-
tive risk.52 Preoperative calculation of the projected     lus.20,65,93,94 Several studies have demonstrated that
indexed EOA can likewise be used to avoid the un-          AVR with a stentless bioprosthesis is associated
warranted use of aggressive procedures such as aortic      with a greater decrease in transvalvular gradient and
root enlargement. The importance of these consider-        LV wall stress, as well as with more complete re-
ations becomes particularly evident in Asian patients,     gression of LV hypertrophy, compared with stented
who often have a small aortic root. This characteris-      valves.18,43,95 Stentless porcine valves were developed
tic is, however, often counterbalanced by the reduced      to help alleviate the problem of PPM by providing a
cardiac output requirement inherent to small body          larger EOA, thus improving flow through the valve
size.85 In this patient population, therefore, the im-     and consequently LV function. 96 Nonetheless, the
plantation of a small prosthesis with a good haemody-      EOA of stentless valves remains somewhat smaller
namic performance often provides a valve EOA that          than that of the corresponding native valve, because
is large enough to accommodate their cardiac output        they are usually implanted using techniques requir-
requirements.7                                             ing insertion of the prosthesis within the patient’s
                                                           aorta.8
                                                                However, the implantation of stentless valves is
Prosthesis with better haemodynamic performance
                                                           more complex than for stented valves, requiring lon-
It is known that, for any aortic annulus size, haemody-    ger cardiopulmonary bypass and ischaemic times.97
namic performance can vary widely from prosthesis to       A study was conducted in 95 patients who underwent
prosthesis. Indeed, haemodynamic performance is gen-       AVR with the Freestyle aortic root prosthesis. The
erally superior, and thus the prevalence and severity of   30-day mortality rate was 3 ± 2% (in-hospital mortal-

46 • HJC (Hellenic Journal of Cardiology)
                                                                   Patient-Prosthesis Mismatch: Alternative Operative Techniques

ity rate 2 ± 2%), with no death being directly valve-        Conclusions
related, while the 1- and 5-year actuarial estimates
                                                             PPM is a risk factor in patients who undergo AVR
of freedom from valve-related morbidity and mortal-
                                                             and is associated with poor haemodynamic and symp-
ity were 82 ± 4% and 79 ± 4%, respectively.98 This
                                                             tomatic status. In patients with PPM, mortality and
prospective analysis demonstrated that the Freestyle
                                                             cardiac events are frequent. Every effort should be
stentless valve can be implanted safely with excellent
                                                             made to avoid severe PPM in all patients, especially
mid-term clinical results. It has superb haemodynam-
                                                             in young patients who are physically active. However,
ics in terms of residual transvalvular pressure gradi-
                                                             PPM may be avoided by using newer generation pros-
ent, EOA, and regression of LV hypertrophy. It is a
                                                             theses, stentless valves or homografts, performing the
valuable alternative for those with a small aortic root,
                                                             Ross procedure, or carrying out aortic annulus en-
particularly in the elderly patient. The question of du-
                                                             largement.
rability compared with conventional stented biopros-
theses remains unanswered and requires longer fol-
low up.98 It was recommended that patients receive
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